Process for copying from polychromic-screen negatives.



A. LEHNER. PROCESS FOR COPYING FROM POLYGHROMIG SCREEN NEGATIVES.

APPLICATION FILED JAN. 17, 1910.

M 9 1 no 1 c 0 d m m a P w j m 6 M v w 5 unrrnn srarns PATENT can-caatrnnnrinnnnn, or HELSTERBACH-ON-THE-MAIN, GERMANY, vAssreuon r0. EAST-MAN KODAK COMPANY, or nocnnsrnn, NEW YORK, A CORPORATION OF NEW YORK.

PROCESS FOR (IJOZPYING FROM POLYGHROMIO-SCREEN NEGATIVES.

Specification of Letters Patent.

Application filed Januar w, 1910. Serial No. 538,5'14.

To all whomit may concern:

Be it known that I, ALFRED LEHNER,

citizen og l (Switzerland, residing a t'Helsterbach-on-t Processes forCopying from Polychromic- Screen Negatives and I do hereby declare thefollowing to bee/full, clear, and exact description of the invention,such as will en-- able others'shilled in the-art to which it appertainsto make and use the same.

It is already known that any desired number of positive copies. can be.made from polychrome screen negatives obtained with parallel linesranged close to one another, it

is only possible to obtain a good picture by crossing the two screens,namely, the negative and the positive, at a certain angle; if this isnot done a cloud or wave pattern will appear in the positive copy. Alsoin the case of three color screens, in .which only one of the threecolors appears as an uniuterrupted line, the other two colors filling upthe intervening space as alternating dots of color, a wave pattern, lessconspicuous that in the above case, will be produced, unless the twoscreens are crossed at a suitable angle, advantageously 45. By thiscross ing at an angle the wave pattern can be avoided, but in practiceit has been found that it is not possible in this way. to obtain acolor-true picture, since the ,color of the uninterrupted lines alwayspredominates, as does also its complementary color, 'while the additionof said uninterrupted lines and the other color elements appearsinadequate. If, for instance, color screens we used in which the redlines are uninterrupted and green and blue fill up the spaces betweenthe red lines in the form of small squares, in the -Main, Germany, haveinvented certain new and useful Improvements in" green and red toneswill be more or less wanting. The cause of this phenomenon has not yetbeen discovered, but I have found means, whereby this disadvantage maybe done away with. The method consists in choosing for the uninterruptedlines of the positive screen one of those colors which in the negativescreen was used fonfilling the intervening spaces between the lines. Ithas gloeen found advantageous to use red as the uninterrupted lines ofthe negative and blue for the uninterrupted lines of the positive.

In the drawing I have illustrated diagrammatically the manner ofcarrying out the process, and as it is im ractical to show in a drawingboth the sensitized coating on the positive and the developed image onthenegative and also the colors of the screen in a single figure, thevarious parts have been shown separated.

The negative screen is indicated by S and the developed image thereon bythe word Negative, the positive screen by S and the emulsion thereon bythe words sensitized surface. The colored portions of the screens are ofcourse greatly magnified and one example of the coloring is illustratedby Patented Oct. 13, 1914.

the conventional shading. Further, the intensity of the colors in thepositive screen may be chosengreater, equal to or less than that of thenegative screen, in order to give the positive picture a greater orlesser brilliancy. Also, in the positive screen the three colorsselected may he dissimilar to those of the negative screen, especiallyin those cases in which a diiierent emulsion is used for negative andpositive. For instance, when a,

highly sensitive emulsion is' used for the negative and a less sensitivesilver-chlorid or chlor-bromid emulsion is used for the positive. 'fAccording to the varying sensitiveness for red, green and blue the colorintensity and absorption of the positive screen will be varied.

According to this process, pictures copied by crossing the screens at anangle Wlll show all color tones equally well. It is, of course,

understood that in the screens referred to as having uninterruptedlines, there are a plurality of such lines of the same color arranged atequal distances apart, as in the usual ruled screens now in use, and inone

